Effect of Climatic Conditions on Flowering of Walnut Genotypes in Romania

The timing and lowering type of walnut genotypes (Juglans regia L.) is one of the important factors that lead to high and constant production. Therefore, the selection of homogame and spring frost tolerant genotypes has been among the most important priorities in breeding programs of walnut. The present paper analyzed the degree of dichogamy and the flowering time of 19 promising genotypes in walnuts from the sandy area, the S-V Oltenia region, Romania. Observations made over two calendar years have shown that the flowering period is influenced by environmental factors, especially temperature. The flowering time has changed from one year to the other, the high temperatures in spring accelerate the evolution of the male flowers,but the female flowers are not greatly influenced by these temperatures. Thus the type of flowering was not constantly, changing according to the climatic conditions of the two years. Knowing the type and timing of flowering of walnut genotypes is very important for pollination, because homogamy types are quite rare in the analyzed population.